Nickel lanthanide alloys for mems packaging applications

ABSTRACT

A semiconductor package including a semiconductor die and at least one bondline positioned on the semiconductor die, the at least one bondline comprising a nickel lanthanide alloy diffusion barrier layer abutting a gold layer.

BACKGROUND

None.

SUMMARY

In accordance with at least one example of the disclosure, asemiconductor package includes a semiconductor die and at least onebondline positioned on the semiconductor die, the at least one bondlinecomprising a nickel lanthanide alloy diffusion barrier layer abutting agold layer. In aspects, the at least one bondline further comprises atleast one other bondline layer, wherein the nickel lanthanide alloydiffusion barrier layer does not alloy with the at least one otherbondline layer. In aspects, the at least one other bondline layercomprises indium, a seed metal, a base metal, or a combination thereof.The base metal can comprise copper and/or the seed metal can comprisetitanium, in aspects. In aspects, the semiconductor die comprises acomplementary metal-oxide semiconductor (CMOS).

In accordance with at least one example of the disclosure, aMicro-Electro-Mechanical System (MEMS) package comprises a semiconductordie, a substrate spaced apart from the semiconductor die, and a bondlinepositioned between and in contact with the semiconductor die and thesubstrate, the bondline comprising a nickel lanthanide alloy diffusionbarrier layer and a gold layer. In aspects, the substrate comprises asemiconductor die. In aspects, the MEMS package further comprises indiumincorporated into the bondline as an interlayer element for transientliquid phase bonding between the gold and the indium. In aspects, thelanthanide comprises cerium, lanthanum, erbium, or a combinationthereof. In aspects, the MEMS package includes a digital micromirrordevice (DMD). In aspects, the MEMS package further comprises one or morelayers comprising a seed metal, a base metal, or both.

In accordance with at least one example of the disclosure, asemiconductor package comprises a nickel lanthanide alloy diffusionbarrier layer, and a gold layer abutting the nickel lanthanide alloydiffusion barrier layer. In aspects, a bondline comprising the nickellanthanide alloy diffusion barrier layer and the gold layer furthercomprises nickel, copper, indium, or a combination thereof. In aspects,the lanthanide comprises cerium, lanthanum, erbium, or a combinationthereof.

In accordance with at least one example of the disclosure, a method offabricating a Micro-Electro-Mechanical System (MEMS) package comprises,for each of two substrates, depositing a nickel lanthanide alloydiffusion barrier layer on the substrate, depositing a gold layer on thenickel lanthanide alloy diffusion barrier layer, aligning outerperimeters of the at least two substrates, with the deposited layersfacing each other, and forming a bondline between the at least twosubstrates via the application of heat, force, or both to the nickellanthanide alloy diffusion barrier layer and the gold layer. In aspects,at least one of the two substrates comprises a wafer. In aspects, themethod further comprises providing one or more additional layers on eachof the at least two substrates prior to depositing the nickel lanthanidealloy diffusion barrier layer. The one or more additional layers cancomprise a seed metal, a base metal, or both. In aspects, the seed metalcomprises titanium, and the base metal comprises copper, or the seedmetal comprises titanium and the base metal comprises copper. The methodcan further comprise depositing the one or more additional layers viachemical vapor deposition (CVD). Depositing of the nickel lanthanidealloy diffusion barrier layer can be effected via reversed pulseelectrodeposition, in aspects. The bondline can further comprise atransient liquid phase bonding between gold and indium.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various examples, reference will now bemade to the accompanying drawings in which:

FIG. 1A shows a Micro-Electro-Mechanical System (MEMS) package inaccordance with various examples;

FIG. 1B shows a digital micromirror device (DMD) package in accordancewith various examples;

FIG. 2 shows a plating stack in accordance with various examples;

FIG. 3A shows a flowchart for a method of fabricating a MEMS package inaccordance with various examples; and

FIG. 3B shows a flowchart for a method of fabricating a MEMS package inaccordance with various examples.

DETAILED DESCRIPTION

Micro-Electro-Mechanical System (MEMS) sensors and actuators arebecoming increasingly common. MEMS packages are utilized to encapsulatesuch MEMS devices to prevent exposure of the external environment tocomponents of the MEMS device via a hermetic seal.

Metals are often utilized in interfaces, such as bondlines, betweensubstrates of MEMS packages. Diffusion of metals within such interfacescan lead to undesirable interaction of metal components. For example,when a gold layer is utilized as a component of a MEMS package interfaceor bondline, diffusion of one or more other metals utilized in theinterface or bondline into the gold layer can lead to an uneconomicaluse of excess gold and potential reliability failures in the interfaceor bondline. As utilized herein, a ‘bondline’ indicates a structureconnecting substrates and sealing a mini-environment around a device(e.g., a MEMS).

Electroplated nickel is widely used as a diffusion barrier layer forMEMS applications. As utilized herein, a ‘diffusion barrier layer’ is alayer that reduces, minimizes, or prevents diffusion of metals betweenmetal layers. However, it is not considered an efficient diffusionbarrier layer. For example, in some hermetic MEMS packagingapplications, a thin layer of pure nickel is coated with a thick layerof gold and bonded in a transient liquid phase process with an indiumcoated wafer. However, the gold in such applications is not onlyconsumed by the indium during bond, but also, over time, by the nickel.The nickel in such a pure nickel diffusion barrier layer not onlyinteracts with the gold, but can also interact with other metals presentin the interface or bondline. For example, a pure nickel diffusionbarrier layer can interact with indium employed for an above-notedtransient liquid phase bond of the gold and indium and can also interactwith a base metal, such as copper, present in the interface or bondline.Another solution to the problem of metal diffusion is the use of puregold as a base metal, which eliminates the use of nickel in theinterface or bondline, but is not economical.

A desirable solution to the metal diffusion problem noted above would bethe discovery of a metallurgy for a diffusion barrier layer that doesnot require a change in the base metal, does not consume gold or othermetals (e.g., indium), and does not alloy with other layers of theinterface or bondline. It has been unexpectedly discovered that the useof a nickel lanthanide alloy rather than pure nickel as a diffusionbarrier layer prevents the inter-diffusion of nickel and gold, allowingmore gold to be available in bond. Due to the reduced consumption ofgold, a reduction in the amount of gold utilized in plating (e.g., areduction in the thickness of gold in the interface or bond) is alsoenabled. Accordingly, the use of a nickel lanthanide alloy diffusionbarrier layer in a MEMS package as per this disclosure provides for thepartial replacement of gold with a nickel lanthanide alloy. Due to thelanthanide alloying element(s), a nickel lanthanide alloy diffusionbarrier layer according to this disclosure provides an efficientdiffusion barrier layer (e.g., prevents inter-diffusion of nickel and/orother metals, such as base metals, into a gold layer), provides enhancedcorrosion resistance, and, by replacing other precious metal platings,can provide cost savings. It is noted that the nickel of theherein-disclosed interface or bond layer is not utilized as a solderingelement in aspects of the herein-disclosed MEMS packages.

According to various examples, a MEMS package of this disclosurecomprises a nickel lanthanide alloy diffusion barrier layer and a goldlayer abutting the nickel lanthanide alloy diffusion barrier layer. TheMEMS package can be utilized to package any MEMS device. By way ofexamples, the MEMS package can be a semiconductor package, such as,without limitation, a digital micromirror device (DMD) package. The MEMSpackage can be hermetic, in aspects. The MEMS package can furthercomprise at least two substrates, with an interface or bondlinetherebetween comprising a nickel lanthanide alloy diffusion barrierlayer as disclosed herein. For example, FIG. 1A depicts a cross sectionview of a MEMS package 10 comprising first substrate 20A and secondsubstrate 20B with bondline 30 therebetween and MEMS 40 positioned onfirst substrate 20A. The bondline comprises at least a gold layer L1abutting a nickel lanthanide alloy diffusion barrier layer L2. The MEMSpackage can be any suitable shape, such as, without limitation,rectangular or square, and the bondline can run along the perimeterthereof. Although indicated on the left and right sides of the crosssection of FIG. 1A, it is to be understood that a bondline may runcontinuously around the perimeter of the MEMS package. The bondline maybe a hermetic bondline around MEMS 40.

First substrate 20A and second substrates 20B can be any suitablesubstrates known to those of skill in the art. According to variousexamples, at least one of first substrate 20A and second substrate 20Bcomprises a semiconductor wafer, such as, without limitation, acomplementary metal-oxide semiconductor (CMOS) wafer. As described indetail hereinbelow, in aspects, the MEMS package is formed bysingulating a wafer into a number of die. In such aspects, the substrateis referred to herein as a wafer prior to singulation and a wafer or diesubsequent singulation. The MEMS package can comprise additionalsubstrates, in various aspects. For example, FIG. 1B shows a MEMSpackage 10A in accordance with various examples of this disclosure. MEMSpackage 10A comprises a first substrate 20A comprising a CMOS wafer 20A,a second substrate 20B comprising a window assembly wafer 2, and a thirdsubstrate 20C comprising a window assembly wafer 1. As utilized herein,a ‘window assembly’ refers to a substrate devised to allow light into aMEMS package. Window wafer assembly 1 can comprise glass, and windowwafer assembly 2 can comprise a silicon wafer, in aspects. Secondsubstrate 20B comprising the window assembly wafer 2 is bonded to firstsubstrate 20A comprising the CMOS wafer via bondline 30A, whichcomprises at least one gold layer L1 abutting a nickel lanthanide alloydiffusion barrier layer L2. In this example, MEMS 40A can comprise aDMD.

The plating stack refers to the plating layers situated between thefirst substrate 20A and the second substrate 20B prior to bonding. Abondline according to this disclosure can be produced via any platingstack comprising a nickel lanthanide alloy diffusion barrier layerdirectly adjacent to (or ‘abutting’) a gold layer. By way ofnon-limiting example, FIG. 2 shows a plating stack 35 in accordance withvarious examples of this disclosure. In the example of FIG. 2, theplating stack 35 comprises a first substrate plating stack 35A on thefirst substrate 20A and a second substrate plating stack 35B on thesecond substrate 20B. First substrate plating stack 35A comprises atitanium/copper layer L3 deposited on first substrate 20A, a nickellanthanide alloy diffusion barrier layer L2 atop the titanium/copperlayer L3, and a gold layer L1 abutting and atop the nickel lanthanidealloy diffusion barrier layer L2. In the example of FIG. 2, the secondsubstrate plating stack 35B comprises a titanium/copper layer L3deposited on second substrate 20B, a nickel lanthanide alloy diffusionbarrier layer L2 atop the titanium/copper layer L3, a gold layer L1abutting and atop the nickel lanthanide alloy diffusion barrier layerL2, and an indium layer L4 atop the gold layer L1. Titanium may be aseed layer for adhesion onto the substrate (e.g., onto a siliconsubstrate), and copper may be the base metal. It is to be understoodthat other seed metals and base metals are within the scope of thisdisclosure.

In aspects, such as depicted in FIG. 2, the first substrate platingstack 35A has a greater width (e.g., an extent in a direction from anouter perimeter of the substrate to a center thereof) W_(A) than a widthW_(B) of the second substrate plating stack 35B. In aspects, the firstsubstrate plating stack 35A has a width W_(A) in a range of from about10 μm to about 700 μm, from about 100 μm to about 600 μm, or from about300 μm to about 400 μm. In aspects, the second substrate plating stack35B has a width W_(B) in a range of from about 10 μm to about 700 μm,from about 100 μm to about 600 μm, or from about 150 μm to about 200 μm.In aspects, a ratio of the width of the first substrate plating stack tothe width of the second substrate plating stack, W_(A)/W_(B), is about1.0, 1.7, or 3.0.

In aspects, the first substrate plating stack 35A has a thickness T_(A)in a range of from about 0.1 μm to about 100 μm, from about 1.0 μm toabout 5.0 μm, or from about 3.5 μm to about 4.0 μm. In aspects, thesecond substrate plating stack has a thickness T_(B) in a range of fromabout 0.1 μm to about 100 μm, from about 1.0 μm to about 20 μm, or fromabout 5.0 μm to about 10.0 μm. In aspects, the ratio of the thickness ofthe first substrate plating stack to the thickness of the secondsubstrate plating stack, T_(A)/T_(B), is about 0.1, 1.0, or 10. Theplating stack 35 of FIG. 2 may be suitable, for example, forapplications in which the MEMS comprises a DMD. Other plating stackscomprising a variety of layers are within the scope of this disclosureand will be apparent to those of skill in the art upon reading thisdisclosure.

In aspects, the nickel lanthanide alloy diffusion barrier layer has athickness in a range of from about 0.1 μm to about 20 μm. In aspects, anickel lanthanide alloy diffusion barrier layer on the first substratehas a thickness in a range of from about 0.1 μm to about 20 μm, fromabout 0.2 μm to about 1.0 μm, or from about 0.25 μm to about 0.5 μm. Inaspects, a nickel lanthanide alloy diffusion barrier layer on the secondsubstrate has a thickness in a range of from about 0.1 μm to about 20μm, from about 0.2 μm to about 1.0 μm, or from about 0.25 μm to about0.5 μm. In aspects, the nickel lanthanide alloy diffusion barrier layerhas a width in a range of from about 300 μm to about 400 μm. In aspects,a width of a nickel lanthanide alloy diffusion barrier layer on thefirst substrate is greater than a width of a nickel lanthanide alloydiffusion barrier layer on the second substrate. In aspects, the nickellanthanide alloy diffusion barrier layer on the first substrate has awidth in a range of from about 10 μm to about 700 μm, from about 100 μmto about 600 μm, or from about 300 μm to about 400 μm. In aspects, thenickel lanthanide alloy diffusion barrier layer on the second substratehas a width in a range of from about 10 μm to about 700 μm, from about100 μm to about 600 μm, or from about 150 μm to about 200 μm. Inaspects, described further hereinbelow with reference to FIG. 3A, anickel lanthanide alloy diffusion barrier layer comprises multiplelayers of deposited nickel lanthanide alloy, for example, 2 or 3. Inaspects, a first layer of nickel lanthanide deposited on the substratehas a grain size in a range of from about 1 nm to about 100 nm, alanthanide content or fraction in a range of from about 0.1 percent byweight (0.1% wt) to about 20% wt, or a combination thereof. In aspects,a second layer of nickel lanthanide deposited on the first layer ofnickel lanthanide alloy deposited on the substrate has a grain size in arange of from about 1 nm to about 100 nm, a lanthanide content orfraction in a range of from about 0.1% wt to about 20% wt, or acombination thereof. In aspects, a third layer of nickel lanthanidedeposited on the second layer of nickel lanthanide alloy deposited onthe substrate has a grain size in a range of from about 1 nm to about100 nm, a lanthanide content or fraction in a range of from about 0.1%wt to about 20% wt, or a combination thereof.

In aspects, the gold layer has a thickness in a range of from about 0.1μm to about 20 μm, from about 1 μm to about 10 μm, or from about 2 μm toabout 5 μm. In aspects, a gold layer on the first substrate has athickness in a range of from about 0.1 μm to about 20 μm, from about 1μm to about 10 μm, or from about 2 μm to about 5 μm. and a gold layer onthe second substrate has a thickness in a range of from about 0.1 μm toabout 20 μm, from about 1 μm to about 10 μm, or from about 2 μm to about5 μm. In aspects, due to the efficiency provided by the herein-disclosednickel lanthanide alloy diffusion barrier layer, a total thickness ofgold deposited in the plating stack (e.g., within first substrateplating stack 35A on first substrate 20A and/or second substrate platingstack 35B on second substrate 20B) is less than a total thickness ofgold utilized with a pure nickel diffusion barrier layer.

FIG. 3A shows a flowchart for a method I of fabricating a MEMS packagein accordance with various examples of this disclosure. Method I offabricating a MEMS package comprises depositing layers of a platingstack on each of two substrates at step 100 and creating a bondlinecomprising a nickel lanthanide alloy diffusion barrier layer abutting agold layer at step 200.

As depicted in FIG. 3A, depositing layers of a plating stack on each oftwo substrates at step 100 comprises depositing a nickel lanthanidealloy diffusion barrier layer at step 120 and depositing a gold layer onthe nickel lanthanide alloy diffusion barrier layer at step 130. Thelanthanide can comprise an element from the lanthanide series ofelements, such as, without limitation, cerium, lanthanum, erbium, or acombination thereof. Depositing a nickel lanthanide alloy diffusionbarrier layer at step 120 can comprise depositing the nickel lanthanidealloy by electroplating. In various aspects, electroplating of thenickel lanthanide alloy diffusion barrier layer can be effected viareversed pulse electrodeposition. The nickel lanthanide alloy diffusionbarrier layer may have the thicknesses, widths, and compositions notedabove.

As indicated in the exemplary flowchart of FIG. 3A, depositing thenickel lanthanide alloy diffusion barrier layer at step 120 can furthercomprise controlling deposition parameters utilized during deposition atstep 122. Controlling deposition parameters at step 122 can be utilizedto control lanthanide alloy deposition to nickel grain boundaries toprevent diffusion of metals to or from other layers (e.g., nickel fromthe nickel lanthanide alloy diffusion barrier layer to the gold layer ora base metal from a base metal layer, such as copper, to the nickellanthanide alloy diffusion barrier layer) along the grain boundaries. Inexamples, the nickel lanthanide alloy diffusion barrier layer cancomprise multiple layers of deposited nickel lanthanide alloy. Inaspects, such multiple layers of deposited nickel lanthanide alloy canbe deposited in a single step via reversed pulse electrodeposition. Themultiple layers of deposited nickel lanthanide alloy of such a nickellanthanide alloy diffusion barrier layer can vary in nickel grain sizeand/or lanthanide alloy content (e.g., a ratio of nickel to lanthanide)to restrict or prevent diffusion of nickel or a base metal such ascopper to the gold layer abutting the nickel lanthanide alloy diffusionbarrier layer. In such applications, the grain size of the nickel and/ora content of nickel lanthanide alloy in the multiple layers of depositednickel lanthanide alloy may increase from a side of the nickellanthanide alloy diffusion barrier layer distal the gold layer to a sideof the nickel lanthanide alloy diffusion barrier layer proximate thegold layer. In aspects, the nickel lanthanide alloy diffusion barrierlayer comprises dislocations, which may also reduce migration of a metaldeposited between the substrate and the nickel lanthanide alloydiffusion barrier layer (e.g., copper from a copper base metal layer) ornickel from the nickel lanthanide alloy diffusion barrier layer to thegold layer. Controlling deposition parameters at step 122 can includecontrolling the deposition to provide a desired number of layers ofnickel lanthanide alloy in the nickel lanthanide alloy diffusion barrierlayer, a grain size throughout the nickel lanthanide alloy diffusionbarrier layer, a content of lanthanide alloy throughout the nickellanthanide alloy diffusion barrier layer, a thickness of the nickellanthanide alloy diffusion barrier layer, or a combination thereof.Deposition parameters include, without limitation, the temperature ofdeposition, a current used for deposition, a chemical makeup of a nickellanthanide alloy bath utilized during deposition (e.g., complexingagent(s) utilized, concentration range), a time of deposition, or acombination thereof.

As depicted in FIG. 3A, depositing layers of a plating stack on each oftwo substrates at step 100 comprises depositing a gold layer on thenickel lanthanide alloy diffusion barrier layer at step 130. The goldlayer may be deposited by electroplating and may have the thicknessesnoted above.

As depicted in FIG. 3A, depositing layers of a plating stack on each oftwo substrates 100 can further comprise preparing each substrate fordeposition of the nickel lanthanide alloy diffusion barrier layer atstep 110. The substrates can be prepared for deposition of the nickellanthanide alloy diffusion barrier layer by any methods known to thoseof skill in the art. In aspects, as indicated in the exemplary flowchartof FIG. 3A, preparing the substrate for deposition of the nickellanthanide alloy diffusion barrier layer at step 110 can compriseproviding a substrate with a seed layer, a base metal layer, or boththereon, or depositing a seed layer, a base metal layer, or both on thesubstrate at step 111. In aspects, a seed layer comprises titanium. Inaspects, a base metal layer comprises copper. In aspects, depositing aseed layer, a base metal layer, or both on the substrate at step 111 iseffected via chemical vapor deposition (CVD). Preparing the substratefor deposition of the nickel lanthanide alloy diffusion barrier layer atstep 110 can further comprise prewetting the substrate at step 112.Prewetting can be effected by any methods known in the art, for examplecleaning with deionized (DI) water.

As indicated in the exemplary flowchart of FIG. 3A, depositing layers ofthe plating stack on each of two substrates at step 100 can furthercomprise depositing, at step 140, one or more additional layers on thegold layer deposited at step 130. For example, in aspects, an indiumlayer is deposited on one of the substrates. Other additional layers arewithin the scope of this disclosure.

As noted above, a method of fabricating a MEMS package according to thisdisclosure comprises creating a bondline comprising a nickel lanthanidealloy diffusion barrier layer abutting a gold layer at step 200. Asdepicted in the flowchart of FIG. 3A, the bondline can be created byaligning the substrates at step 210 and subjecting the alignedsubstrates to temperature and/or bond force to melt the plating stackand form the bondline at step 220. Aligning the substrates at step 210can comprise aligning the outer perimeters of the two wafers with thedeposited layers of the first substrate contacting the deposited layersof the second substrate stack. Subjecting to temperature and/or bondforce at step 220 to form the bondline can comprise subjecting thealigned substrates to a temperature in a range of from about 25° C. toabout 350° C., from about 100° C. to about 250° C., or from about 175°C. to about 200° C., a bond force in the range of from about 0.1 kN toabout 100 kN, from about 5 kN to about 40 kN, or from about 10 kN toabout 20 kN, or a combination thereof. In applications, the methodproduces a wafer stack assembly for singulation. Other steps may beincluded in the method, for example between the plating of thesubstrates and substrate bonding (e.g., between steps 100 and 200). TheMEMS, such as a DMD, may be incorporated into the MEMS package viastandard semiconductor packaging steps following the bond process.Without limitation, such steps may include, for example, singulation,die attach, encapsulation, wire bond, etc.

FIG. 3B shows a flowchart for a method IA of fabricating a MEMS packagein accordance with various examples. Method IA comprises depositinglayers of a first substrate plating stack on a first substrate at step100A and depositing layers of a second substrate plating stack on asecond substrate at step 100B. In specific aspects, one of the firstsubstrate and the second substrate is a CMOS wafer and the othersubstrate comprises a window assembly. As depicted in the exemplaryflowchart of FIG. 3B, depositing layers of a first substrate platingstack on a first substrate at step 100A and depositing layers of asecond substrate plating stack on a second substrate at step 100Bcomprise nickel lanthanide plating at steps 120A and 120B, respectively,and gold plating at steps 130A and 130B, respectively. Depositing layersof the first substrate plating stack on the first substrate at step 100Aand depositing layers of the second substrate plating stack on thesecond substrate at step 100B can further comprise providing an incomingwafer assembly with a titanium/copper layer at steps 111A and 11B,respectively and/or prewetting prior to nickel lanthanide plating atsteps 112A and 112B, respectively. In specific applications, depositinglayers of a plating stack on the first substrate at step 100A furthercomprises indium plating at step 140A. The indium layer of the platingstack may be utilized to form an intermetallic between gold and indiumvia transient liquid phase bonding. In some aspects, a width of aplating stack comprising indium is less than a width of a plating stacknot comprising indium to prevent indium from extending beyond thebondline during bonding at step 200.

Method IA further comprises wafer bonding at step 200 to bond thesubstrates and thus produce a stack assembly for singulation. Thebonding may be effected as described hereinabove with reference to step200 of the exemplary flowchart of FIG. 3A. Again, as noted above, othersteps may be included in the method, for example between the plating ofthe substrates and substrate bonding.

In the foregoing discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . .” Unlessotherwise stated, “about,” “approximately,” or “substantially” precedinga value means+1-10 percent of the stated value.

The above discussion is meant to be illustrative of the principles andvarious aspects of the present disclosure. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

What is claimed is:
 1. A semiconductor package comprising: a semiconductor die; and at least one bondline positioned on the semiconductor die, the at least one bondline comprising a nickel lanthanide alloy layer abutting a gold layer.
 2. The semiconductor package of claim 1, wherein the at least one bondline further comprises at least one other bondline layer, wherein the nickel lanthanide alloy layer does not alloy with the at least one other bondline layer.
 3. The semiconductor package of claim 2, wherein the at least one other bondline layer comprises indium, a seed metal, a base metal, or a combination thereof.
 4. The semiconductor package of claim 3, wherein the base metal comprises copper, and wherein the seed metal comprises titanium, or both.
 5. The semiconductor package of claim 1, wherein the semiconductor die comprises a complementary metal-oxide semiconductor (CMOS).
 6. A Micro-Electro-Mechanical System (MEMS) package, comprising: a semiconductor wafer; a substrate spaced apart from the semiconductor wafer; and a bondline positioned between and in contact with the semiconductor wafer and the substrate, the bondline comprising a nickel lanthanide alloy layer and a gold layer.
 7. The MEMS package of claim 6, wherein the substrate comprises a semiconductor wafer.
 8. The MEMS package of claim 6 further comprising indium incorporated into the bondline as an interlayer element for transient liquid phase bonding between the gold and the indium.
 9. The MEMS package of claim 6, wherein the lanthanide comprises cerium, lanthanum, erbium, or a combination thereof.
 10. The MEMS package of claim 6, wherein the gold layer has a thickness in a range of from about 0.1 μm to about 20 μm.
 11. The MEMS package of claim 6, further comprising one or more layers comprising a seed metal, a base metal, or both.
 12. A semiconductor package comprising: a structure electrically connecting two substrates, comprising: a nickel lanthanide alloy layer; and a gold layer abutting the nickel lanthanide alloy layer.
 13. The semiconductor package of claim 12, wherein a bondline comprising the nickel lanthanide alloy layer and the gold layer further comprises nickel, copper, indium, or a combination thereof.
 14. The semiconductor package of claim 13, wherein the lanthanide comprises cerium, lanthanum, erbium, or a combination thereof.
 15. A method of fabricating a Micro-Electro-Mechanical System (MEMS) package, the method comprising: for each of two substrates: depositing a nickel lanthanide alloy layer on the substrate; depositing a gold layer on the nickel lanthanide alloy layer; aligning outer perimeters of the at least two substrates, with the deposited layers facing each other; forming a bondline between the at least two substrates via the application of heat, force, or both to the nickel lanthanide alloy layer and the gold layer; and singulating to produce the MEMS package.
 16. The method of claim 15, wherein at least one of the two substrates comprises a wafer.
 17. The method of claim 15 further comprising providing one or more additional layers on each of the at least two substrates prior to depositing the nickel lanthanide alloy layer.
 18. The method of claim 17, wherein the one or more additional layers comprise a seed metal, a base metal, or both.
 19. The method of claim 18, wherein the seed metal comprises titanium, and wherein the base metal comprises copper, or wherein the seed metal comprises titanium and the base metal comprises copper.
 20. The method of claim 18 further comprising depositing the one or more additional layers via chemical vapor deposition (CVD).
 21. The method of claim 15, wherein the depositing of the nickel lanthanide alloy layer is effected via reversed pulse electrodeposition.
 22. The method of claim 15, wherein the bondline further comprises a transient liquid phase bonding between gold and indium. 